1. Field of the Invention
The present invention relates to a temperature measuring device which is positioned within the airflow flowing into an engine of an aircraft or an external surface of the aircraft, and which measures the temperature of the airflow.
2. Description of the Related Art
Conventionally, on aircraft on which engines are mounted, temperature measuring devices which measure the temperature of airflows are arranged in the air intake or near the intake of the engines, or on an external surface of the aircraft.
The air to the outside of a cruising aircraft forms an airflow at high speed, and it is necessary to measure the total temperature of this airflow. In order to measure the total temperature of the airflow, for example, a temperature measuring device having a structure in which the airflow is guided into a casing having a sensor located inside, a stagnation point in the airflow is formed by the airflow striking the inner surface of the casing and the stagnation temperature at this stagnation point is measured. Alternatively, a temperature measuring device having a structure in which the total temperature is measured by means of restricting the flow rate of the airflow passing through a passage can be used.
In addition, in Japanese Patent Application No. Hei 11-95563 previously filed by the applicant of the present application, a temperature measuring device in which a sensor is provided in the surface of a blade-shaped casing is described. Under practical conditions, this temperature measuring device derives the total temperature by measuring the temperature of the airflow passing over the surface of the casing from the fact that the temperature of the airflow passing over the surface of the casing and causing friction approximates the total temperature at the stagnation point.
However, when an aircraft is cruising in conditions of ice and snow, with the above-mentioned temperature measurement device having a structure in which the airflow strikes the inner wall of the casing, there is the problem that since the ice and snow adhere to and build up inside the casing and on the periphery of the air intake, the air intake becomes blocked, the airflow cannot be guided into the air intake, and it is not possible for the temperature to be measured. In addition, there is the problem that ice and snow adhere to the sensor, accurate temperature measurement is prevented, and the sensor itself becomes damaged. In the same way, the temperature measurement device which has a structure through which the airflow passes also has the problem that the passage becomes blocked by the adhesion of ice and snow, and temperature measurement becomes impossible.
In addition, according to the temperature measurement device described in Japanese Patent Application No. Hei 11-95563, a structure is adopted in which the adhesion and build up of ice and snow on the sensor or in the vicinity of the sensor does not occur. Therefore, problems such as the sensor becoming damaged, or accurate temperature measurement being prevented have been solved. However, when lumps of ice and snow which adhere to the casing become large and detach, these lumps of ice and snow strike the engine. the airframe or equipment of the aircraft, due to the airflow. Therefore, there is the problem that the engine, aircraft or the like will become damaged. It is possible to prevent the icing which causes this type of problem by heating the casing using an electric heater or high temperature engine bleed air, but the structure becomes complex and heavy, and accurate temperature measurement is difficult when the casing is heated.